1. Field of the Invention
The present invention relates to a plasma processing apparatus and a plasma processing method for generating plasma using electron cyclotron resonance (ECR) by a microwave and a magnetic field and processing a substrate, for example, a semiconductor wafer on the basis of the plasma.
2. Description of the Related Art
A plasma processing apparatus using ECR generates microwave of, for example, 2.45 GHz into a vacuum plasma processing chamber via a wave guide, at the same time, applies a magnetic field of, for example, 875 gauss by, for example, an electromagnetic coil, converts plasma generation gas to high-concentration plasma by the mutual action (resonance) of the microwave and magnetic field, and performs the film depositing process and etching process on the basis of this plasma.
On the other hand, from the requests of footprint reduction and cut-down of cost, an apparatus for airtightly connecting a plurality of plasma processing units to a common transfer chamber and accessing each plasma processing unit by a transfer arm in the transfer chamber has been developed. FIG. 6 shows an appearance of such a kind of apparatus. In this specification, plasma processing units 1A and 1B connected to a transfer chamber 10 are called plasma processing units and the whole is called a plasma processing apparatus.
Each of the plasma processing units 1A and 1B has a vacuum processing chamber 13 including a first vacuum chamber 11 composed of a small-diameter cylinder and a second vacuum chamber 12 composed of a large-diameter cylinder, a wave guide 14 which is connected to the top of the first vacuum chamber 11 via a microwave transmission window not shown in the drawing and leading a microwave into the vacuum processing chamber 13, for example, in the TM mode, and a microwave generator 14a installed at the base end of the wave guide 14. A wafer W transferred onto a mounting stage not shown in the drawing in the second vacuum chamber 12 from the transfer chamber 10 is processed by plasma.
The wave guide 14 is composed of a conical wave guide positioned above the first vacuum chamber 11 which is widen toward the end, a cylindrical wave guide 16 connected on the conical wave guide 15, and a rectangular wave guide 17 connected perpendicularly to the side of the cylindrical wave guide 16. FIG. 7 is a schematic plan view showing the location relationship between the wafer W on the mounting stage and the rectangular wave guide 17 when the plasma processing apparatus shown in FIG. 6 is viewed from the top. The wave guide 14 and the microwave generator 14a are indicated by dotted lines. As shown in FIGS. 6 and 7, both of the rectangular wave guide 17 of the plasma processing unit 1A and the rectangular wave guide 17 of the plasma processing unit 1B are hook-shaped and arranged symmetrically right and left, that is, symmetrically about the center axis line of the transfer chamber 10 in the horizontal direction. In FIG. 7, numeral 10a indicates a transfer arm, which transfers, for example, the wafer W positioned outside the transfer chamber 10 to the mounting stages of the plasma processing units 1A and 1B.
In the aforementioned apparatus, since the wafer W is positioned, in both plasma processing units 1A and 1B, for example, the V-shaped notch for positioning the wafer W is directed toward the rotational center P of the transfer arm 10a. On the other hand, the rectangular wave guides 17 of the plasma processing units 1A and 1B are positioned symmetrically right and left, so that the positions of the rectangular wave guides 17 for the direction of the wafer W are different from each other.
A microwave is propagated through the rectangular wave guide 17 in the TE mode and the TE mode is converted to the TM mode at the connector with the cylindrical wave guide 16. In the cylindrical wave guide 16, the electric field intensity distribution should be originally concentrically (the direction of the electric field is the direction of the diameter). However, the distribution is actually one-sided. FIG. 8 is a drawing for showing this situation schematically and the numbers (1) to (5) stated in the drawing indicate the intensity of each of the divided areas. A smaller number among the numbers (1) to (5) indicates weaker intensity of the electric field.
As the microwave moves toward the mounting stage, the degree of deviation of the electric field is reduced. However, in a state that there is a deviation of the electric field at the ECR point where ECR is generated, high-concentration plasma is generated, so that the plasma concentration distribution (concentration distribution of ions and electrons) is also deviated from the concentric state. Therefore, viewed from the wafer W, the degree of deviation of the plasma concentration is different between the plasma processing units 1A and 1B, so that the processing condition in the surface of the wafer W is different between them. For example, when the film forming process is performed, the film thickness distribution is different and for example, when the etching process is performed, variations in the degree of grooving are different.
As mentioned above, when the effect of deviation of a microwave in the TM mode, that is, the effect of the electric field intensity distribution is different between the plasma processing units 1A and 1B and as a result, there is a difference in the processing condition of the wafer W, for example, when the processing condition is bad, the analysis of the cause and subsequent adjustment and improvement are complicated and hard to be carried out and the management of each unit is difficult.
The present invention was developed with the foregoing in view and is intended to provide an apparatus and method for eliminating differences in the processing condition of a substrate between the plasma processing units.
The present invention provides a plasma processing apparatus comprising: a plurality of plasma processing units, each having a vacuum processing chamber including a mounting stage for mounting a substrate with a reference point and a wave guide for introducing high frequency waves into this vacuum processing chamber for converting process gas to plasma by high frequency waves and processing the substrate by the plasma; and a common transfer chamber which is airtightly connected to these plurality of plasma processing units and includes a transfer arm for transferring the substrate to the mounting stage in the fixed transfer direction and in a state that the reference point of the substrate is positioned with respect to the transfer arm, wherein between the plasma processing units, the location relationship of the wave guide to the transfer direction of the transfer arm is the same.
The process to be performed for the substrate is, for example, the film forming process and etching process.
According to the present invention, the reference point of the substrate is positioned against the transfer arm and the location of each wave guide of each plasma unit in relation to the transfer direction of the transfer arm is the same for each plasma processing apparatus, so that the location of the wave guide relative to the reference point of the substrate is the same between the plasma processing units. Therefore, even if the electric field intensity distribution of high frequency waves introduced from the wave guide is deviated and the plasma concentration on the basis of it is not uniform, there is no difference in the effect of the deviation of the electric field intensity distribution for the substrate between the plasma processing units. Therefore, analysis of the processing condition and improvement of the apparatus can be easily carried out.
The present invention provides a plasma processing method for performing a predetermined process for a substrate by a plasma processing apparatus comprising a plurality of plasma processing units, each having a vacuum processing chamber including a mounting stage for mounting a substrate with a reference point and a wave guide for introducing high frequency waves into this vacuum processing chamber for converting process gas to plasma by high frequency waves and processing the substrate by the plasma and a common transfer chamber which is airtightly connected to these plurality of plasma processing units and includes a transfer arm for transferring the substrate to the mounting stage in the fixed transfer direction comprises the steps of: transferring the substrate with a reference point to the mounting stages of the plasma processing units from the transfer chamber and making the location relationship between the reference point of the substrate to be mounted on the mounting stage to the wave guide equal between the plasma processing units and, performing the plasma process for the substrate in a state that the location relationship of the reference value of the substrate to be mounted on the mounting stage to the wave guide is kept the same between the plasma processing units.